Warren, a Harvard law professor and consumer advocate, is running on the Democratic ticket against U.S. Senator Scott Brown.

Her legal work was scrutinized at last week's debate when Brown assailed her for claiming she had worked for asbestos victims. In fact, she represented the insurance company Travelers in its quest to gain immunity from asbestos suits in exchange for setting aside $500 million for asbestos victims, Boston.com reported Friday.

Warren, who successfully argued the asbestos case before the Supreme Court, said in a statement Monday that she never claimed that she had a law license in Massachusetts or "hung out a shingle" there.

Warren has a license to practice in federal courts and the Supreme Court and never broke any laws, according to her campaign.

"This is a distraction from the real issues," spokeswoman Julie Edwards said.